Fix a bunch of clazy warnings

Should be uncontroversial and compile time checked.

applets/systemmonitor/systemmonitor/systemmonitor.cpp

@@ -40,7 +40,7 @@ SystemMonitor::SystemMonitor(QObject *parent, const QVariantList &args)
 
     //Don't set the preset right now as we can't write on the config here because we don't have a Corona yet
     if (args.count() > 2 && args.mid(3).length() > 0) {
-        const QString preset = args.mid(3).first().toString();
+        const QString preset = args.mid(3).constFirst().toString();
         if (preset.length() > 0) {
             m_pendingStartupPreset = preset;
         }

components/shellprivate/interactiveconsole/interactiveconsole.cpp

@@ -275,7 +275,7 @@ void InteractiveConsole::loadScript(const QString &script)
 void InteractiveConsole::showEvent(QShowEvent *)
 {
     if (m_editorPart) {
-        m_editorPart->views().first()->setFocus();
+        m_editorPart->views().constFirst()->setFocus();
     } else {
         m_editor->setFocus();
     }
@@ -336,7 +336,7 @@ void InteractiveConsole::openScriptUrlSelected(int result)
     }
 
     if (result == QDialog::Accepted) {
-        const QUrl url = m_fileDialog->selectedUrls().first();
+        const QUrl url = m_fileDialog->selectedUrls().constFirst();
         if (!url.isEmpty()) {
             loadScriptFromUrl(url);
         }
@@ -452,7 +452,7 @@ void InteractiveConsole::saveScriptUrlSelected(int result)
     }
 
     if (result == QDialog::Accepted) {
-        const QUrl url = m_fileDialog->selectedUrls().first();
+        const QUrl url = m_fileDialog->selectedUrls().constFirst();
         if (!url.isEmpty()) {
             saveScript(url);
         }
@@ -551,7 +551,7 @@ void InteractiveConsole::evaluateScript()
         if (reply.type() == QDBusMessage::ErrorMessage) {
             print(reply.errorMessage());
         } else {
-            const int id = reply.arguments().first().toInt();
+            const int id = reply.arguments().constFirst().toInt();
             QDBusConnection::sessionBus().connect(s_kwinService, "/" + QString::number(id), QString(), QStringLiteral("print"), this, SLOT(print(QString)));
             QDBusConnection::sessionBus().connect(s_kwinService, "/" + QString::number(id), QString(), QStringLiteral("printError"), this, SLOT(print(QString)));
             message = QDBusMessage::createMethodCall(s_kwinService, "/" + QString::number(id), QString(), QStringLiteral("run"));

components/shellprivate/widgetexplorer/plasmaappletitemmodel.cpp

@@ -112,7 +112,7 @@ QString PlasmaAppletItem::author() const
         return QString();
     }
 
-    return m_info.authors().first().name();
+    return m_info.authors().constFirst().name();
 }
 
 QString PlasmaAppletItem::email() const
@@ -121,7 +121,7 @@ QString PlasmaAppletItem::email() const
         return QString();
     }
 
-    return m_info.authors().first().emailAddress();
+    return m_info.authors().constFirst().emailAddress();
 }
 
 int PlasmaAppletItem::running() const

kcms/cursortheme/kcmcursortheme.cpp

@@ -209,7 +209,6 @@ void CursorThemeConfig::updateSizeComboBox()
     if (selected.isValid()) {
         const CursorTheme *theme = m_themeProxyModel->theme(selected);
         const QList<int> sizes = theme->availableSizes();
-        QIcon m_icon;
         // only refill the combobox if there is more that 1 size
         if (sizes.size() > 1) {
             int i;
@@ -384,8 +383,6 @@ void CursorThemeConfig::load()
 {
     ManagedConfigModule::load();
     setPreferredSize(cursorThemeSettings()->cursorSize());
-    // Get the name of the theme KDE is configured to use
-    QString currentTheme = cursorThemeSettings()->cursorTheme();
 
     // Disable the listview and the buttons if we're in kiosk mode
     if (cursorThemeSettings()->isImmutable( QStringLiteral( "cursorTheme" ))) {

kcms/fonts/fontsaasettings.cpp

@@ -67,7 +67,6 @@ class FontAASettingsStore : public QObject
 public:
     FontAASettingsStore(FontsAASettings *parent = nullptr)
         : QObject(parent)
-        , m_settings(parent)
     {
         load();
     }
@@ -243,7 +242,6 @@ public:
     }
 
 private:
-    FontsAASettings *m_settings;
     bool m_isImmutable;
     bool m_antiAliasing;
     bool m_antiAliasingChanged;

kcms/fonts/kxftconfig.cpp

@@ -648,7 +648,6 @@ void KXftConfig::readContents()
                         while (en.isComment()) {
                             en = en.nextSibling();
                         }
-                        QString  family;
                         double   from = -1.0,
                                  to = -1.0,
                                  pixelFrom = -1.0,

kcms/kfontinst/lib/Fc.cpp

@@ -387,7 +387,6 @@ QString getFcString(FcPattern *pat, const char *val, int index)
 // ...so if possible, use that. Else, use the first non "xx" lang.
 QString getFcLangString(FcPattern *pat, const char *val, const char *valLang)
 {
-    QString rv;
     int     langIndex=-1;
 
     for(int i=0; true; ++i)

kcms/kfontinst/lib/FcEngine.cpp

@@ -568,6 +568,9 @@ void cleanupXImage(void *data)
 
 QImage CFcEngine::Xft::toImage(int w, int h) const
 {
+    Q_UNUSED(w)
+    Q_UNUSED(h)
+
     if (!XftDrawPicture(itsDraw)) {
         return QImage();
     }

kcms/kfontinst/lib/Misc.cpp

@@ -419,8 +419,7 @@ QMap<QString, QString> getFontFileMap(const QSet<QString> &files)
         {
             QVector<QString>             orig(fIt.value().count()),
                                          modified(fIt.value().count());
-            QSet<QString>::ConstIterator oIt(fIt.value().constBegin()),
-                                         oEnd(fIt.value().constEnd());
+            QSet<QString>::ConstIterator oIt(fIt.value().constBegin());
             bool                         good=true;
             int                          count=fIt.value().count();
 

kcms/lookandfeel/lnftool.cpp

@@ -71,7 +71,7 @@ int main(int argc, char **argv)
     }
     
     if (parser.isSet(_list)) {
-        QList<KPluginMetaData> pkgs = KPackage::PackageLoader::self()->listPackages("Plasma/LookAndFeel");
+        const QList<KPluginMetaData> pkgs = KPackage::PackageLoader::self()->listPackages("Plasma/LookAndFeel");
 
         for (const KPluginMetaData &data : pkgs) {
             std::cout << data.pluginId().toStdString() << std::endl;

ksmserver/server.cpp

@@ -590,7 +590,7 @@ extern "C" int _IceTransNoListen(const char * protocol);
 #endif
 
 KSMServer::KSMServer(InitFlags flags)
-  : sessionGroup( QStringLiteral( "" ) )
+  : sessionGroup(QLatin1String(""))
   , m_kwinInterface(new OrgKdeKWinSessionInterface(QStringLiteral("org.kde.KWin"), QStringLiteral("/Session"), QDBusConnection::sessionBus(), this))
   , sockets{ -1, -1 }
 {
@@ -847,7 +847,7 @@ QString KSMServer::currentSession()
 {
     if ( sessionGroup.startsWith( QLatin1String( "Session: " ) ) )
         return sessionGroup.mid( 9 );
-    return QStringLiteral( "" ); // empty, not null, since used for KConfig::setGroup // TODO does this comment make any sense?
+    return QLatin1String(""); // empty, not null, since used for KConfig::setGroup // TODO does this comment make any sense?
 }
 
 void KSMServer::discardSession()

logout-greeter/shutdowndlg.cpp

@@ -164,7 +164,6 @@ void KSMShutdownDlg::init()
     rootContext()->setContextProperty(QStringLiteral("screenGeometry"), screen()->geometry());
 
     QString fileName;
-    QString fileUrl;
     KPackage::Package package = KPackage::PackageLoader::self()->loadPackage(QStringLiteral("Plasma/LookAndFeel"));
     KConfigGroup cg(KSharedConfig::openConfig(QStringLiteral("kdeglobals")), "KDE");
     const QString packageName = cg.readEntry("LookAndFeelPackage", QString());

runners/bookmarks/browsers/chrome.cpp

@@ -54,7 +54,7 @@ Chrome::Chrome( FindProfile* findProfile, QObject* parent )
         m_profileBookmarks << new ProfileBookmarks(profile);
         m_watcher->addFile(profile.path());
     }
-    connect(m_watcher, &KDirWatch::created, [=] { m_dirty = true; });
+    connect(m_watcher, &KDirWatch::created, this, [this] { m_dirty = true; });
 }
 
 Chrome::~Chrome()